remove entryComponents prop from metadata

[Quramy]

Issue:

It seems that entryComponents is not reeded the Angular example's story.
It's misleading and users may think entryComponents is required to use template.

What I did

• remove the prop from example stories' metadata

[codecov]

Codecov Report

Merging #2790 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #2790   +/-   ##
=======================================
  Coverage   35.51%   35.51%           
=======================================
  Files         434      434           
  Lines        9501     9501           
  Branches      997     1019   +22     
=======================================
  Hits         3374     3374           
+ Misses       5455     5440   -15     
- Partials      672      687   +15

Impacted Files	Coverage Δ
app/polymer/src/server/config/babel.js	0% <0%> (-100%)	⬇️
app/polymer/src/server/babel_config.js	0% <0%> (-76.67%)	⬇️
lib/ui/src/modules/ui/routes.js	0% <0%> (ø)	⬆️
lib/core/src/client/preview/config_api.js	46.55% <0%> (ø)	⬆️
addons/events/src/components/Event.js	38.55% <0%> (ø)	⬆️
addons/viewport/src/components/RotateViewport.js	22.72% <0%> (ø)	⬆️
addons/info/src/components/PropTable.js	87.23% <0%> (ø)	⬆️
lib/ui/src/modules/ui/containers/layout.js	12.5% <0%> (ø)	⬆️
...ddons/actions/src/containers/ActionLogger/index.js	49.25% <0%> (ø)	⬆️
lib/ui/src/modules/ui/components/shortcuts_help.js	12.85% <0%> (ø)	⬆️
... and 56 more

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